Primary amines sulphonyl derivatives

Z>) Toluene-p-sulphonylotion (p. 247). Proceed as in 3(a), but using 1 5 g of toluene-p-sulphonyl chloride, either finely pow dered or in concentrated acetone solution. Note. The sulphonyl derivative of a primary amine is soluble in aqueous sodium hydroxide, and the final solution must be diluted and acidified to precipitate the product. Recrystallise and take the m.p. (M.ps., pp. 550-551.)... 

Note. PRIMARY ALIPHATIC AMINES. The lower amines are gases or low-boiling liquids (b.ps. CHjNH, 7 CiHjNH, 17 CH,(CH2,>,NH 49 (CHg)jCHNHa, 34 ) but may be encountered in aqueous or alcoholic solution, or as their crystalline salts. They are best identified as their benzoyl, or toluene-/>-sulphonyl derivatives (c/. (C) above), and as their picrates when these are not too soluble. This applies also to benzylamine, CjHsCHjNH, b.p. 185 also to ethylenediamine, usually encountered as the hydrate, NHj (CHj)j NH2,HjO, b.p. 116 , for which a moderate excess of the reagent should be used to obtain the di-acyl derivative. (M.ps., pp. 55 55 )... 

Phenylurea Derizatives. These are prepared precisely as those from primary amines, except that the toluene-/)-sulphonyl and benzene sulphonyl derivatives are insoluble in aqueous sodium hydroxide and therefore separate on formation. (M.ps., p. 552.)... 

Primary and Secondary Amines. Picrates (pp. 374, 376), Acetyl derivatives (pp. 373, 376), Benzoyl derivatives (pp. 374, 376), Toluene-p-sulphonyl and benzene-sulphonyl derivatives (pp. 374, 376), Phenylurea derivatives (pp. 374, 377)-... 

If the presence of a disulphonyl derivative from a primary amine is suspected (e.., formation of a precipitate in alkaline solution even after dilution), reflux the precipitate, obtained after acidifyim , with a solution of I g. of sodium in 20 ml. of rectifled spirit for 15 minutes. Evaporate the alcohol, dilute with water, and filter if necessary acidify with dilute hydrochloric acid. Collect the sulphonyl derivative and recrystallise it from alcohol or dilute alcohol. 

The Schotten-Baumann reaction can also be applied to primary and secondary aromatic amines (see p. 303) it is much used in the identification of compounds to which it can be applied, by the preparation of their benzoyl, phenylacetyl, or benzene sulphonyl derivatives. 

Dissimilarity with Benzoylation. It has been observed that there is one vital difference between the benzoyl and the sulphonyl derivatives of amines. Importantly, when the primary- and secondary-samnes are made to react with Benzoyl Chloride, it gives rise to mono-and di-substituted structural analogues of benzamide and when subjected to treatment with Benzenesulphonyl Chloride, 3neld similar derivatives of benzene sulphonamide. 

Hinsberg s separation of amines. A mixture of primary, secondary and tertiary amines may be separated by treatment with p-toluene-sulphonyl chloride, which reacts with primary amines to give mono-sulphonyl derivatives soluble in alkali, and converts secondary amines to alkali-insoluble sulphonyl derivatives, but does not react with tertiary amines. 

An excellent discussion on derivatization techniques has been given by Lawrence (17) including a detailed discussion on pre-column derivatization (18) and post-column derivatization (19). Probably, the more popular procedures are those that produce fluorescing derivatives to improve detector sensitivity. One of the more commonly used reagents is dansyl chloride (20), 5-dimethylamino-naphthalene-1-sulphonyl chloride (sometimes called DNS-chloride or DNS-C1). The reagent reacts with phenols and primary and secondary amines under slightly basic conditions forming sulphonate esters or sulphonamides. 

These sulphonyl chlorides form derivatives with primary and secondary amines useful for identification purposes. 

The Michael-type addition, a nucleophilic addition of an anion to the carbon-carbon double bond of an a,(3-unsaturated ketone, aldehyde, nitrile, nitro, sulphonyl, or carboxylic acid derivative, provides a powerful tool for carbon-carbon bond formation. The reaction is most successful with relatively nonbasic ( soft ) nucleophiles such as thiols, cyanide, primary and secondary amines, and P-dicarbonyl compounds. There is often a competition between direct attack on the carbonyl carbon (1,2-addition) and conjugate addition (1,4-addition) when the substrate is an a,(3-unsaturated carbonyl compound. 

The classical route to derivatives for identifying sulphonic acids/sulphonates is via formation of the sulphonyl chlorides and then converting them to amides with ammonia or a primary or secondary amine. 

Dansyl chloride (DNS-Cl) (l-dimethylaminonaphthalene-5-sulphonyl-chloride). This reagent was originally introduced into protein chemistry for end-group analysis over twenty years ago (Gray and Hartley, 1963) and has been widely used because of the simplicity of the reaction and its ability to react with both primary and secondary amines, unlike OPA and fluram. Furthermore, in contrast to other fluorescent reagents, the dansyl derivatives are stable to acid hydrolysis, and can therefore be used in N-group labelling before hydrolysis. HPLC separations of dansyl derivatives have recently been published (Tapuhi et al., 1981). Sensitivity of detection is at the low picomole level. The sensitivity is limited because of the side-reactions which can occur with lysine and, to a lesser extent, histidine and tyrosine. 

Similarity with Benzoylation. The most significant point of similarity between benzoylation and sulphonylation is that both of them may be used to accomplish reasonably well defined crystalline derivatives not only of hydroxyl compounds but also of primary and secondary amines. [Note. It is, however, pertinent to observe here that the tertiary amines cannot be subjected to sulphonylation.]... 

R, S )-2-(p-Chlorophenyl )-a-methyl-5-benzoxazoleacetyl chloride can be used similarly to chloroformates and sulphonyl chlorides. It reacts with primary and secondary amines and with alcohols. Excitation and emission maxima are at 310 nm and 365 nm, respectively. Solvents for the TLC and HPLC separation the derivatives of a number of amines and drugs have been reported [191]. 

An excellent and detailed discussion of pre-column and post column derivatization has been given by Lawrence (11) and includes a comprehensive list of available reagents, procedures and application examples. One of the more popular procedures is fluorescence derivatization and probably the most popular fluorescent reagent is dansyl chloride (12). 5-Dimethylamino-naphthalene-l-sulphonyl chloride (dansyl chloride, DNS-chloride or DNS-Cl) reacts with phenols and primary and secondary amines under slightly basic conditions to form a fluorescent sulphonate ester or sulphonamide. The quantum efficiency of dansyl derivatives is high whereas the reagent itself does not fluoresce. 

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